The present invention relates to improvements in apparatus for ascertaining certain characteristics of substantially rod-shaped commodities. More specifically, the invention relates to improvements in apparatus which can be utilized to ascertain the mass and/or the moisture content of rod-shaped commodities which are moved length-wise through the internal chamber of a housing wherein successive increments of the moving commodities are subjected to the action of microwaves. The commodities constitute, or can constitute, rod-shaped products of the tobacco processing industry, for example, rod-like fillers of shredded tobacco of the type contained in plain or filter cigarettes, cigarillo tobacco or cigar tobacco. Furthermore the commodities can constitute wrapped fillers constituting filter material (such as paper and/or cellulose acetate) for tobacco smoke.
Commonly owned published European patent application Serial No. 0 791 823 A2 and the corresponding U.S. Pat. No. 6,163,158 disclose an apparatus wherein a continuous rod (such rod can comprise a filler of shredded tobacco confined in a tubular envelope of cigarette paper) is caused to advance through a resonator housing having an internal chamber where the rod is subjected to the action of microwaves in order to ascertain the mass and/or the moisture content of the filler. The resonator housing consists of a metallic material. Changes of the characteristics of the microwaves which have been influenced by the moving rod in the internal chamber of the resonator housing are evaluated by one or more suitable circuits (such circuit or circuits can also ascertain the characteristics of the microwaves when the internal chamber of the resonator housing is empty) for the purpose of ascertaining and furnishing information pertaining to the mass and/or the moisture content of unit lengths of the moving rod.
An object of the invention is to provide a novel and improved resonator housing for use in apparatus of the type disclosed in the published European patent application Serial No. 0 791 823 A2.
Another object of the invention is to provide a resonator housing which contributes to the accuracy and/or sensitivity of the apparatus.
A further object of the invention is to provide the apparatus with novel and improved apparatus for defining a path for lengthwise movement of rod-shaped commodities through the internal chamber of the resonator housing.
An additional object of the invention is to provide novel and improved apparatus for maintaining the temperature of the resonator housing within an optimum range to ensure highly accurate measurements pertaining to the mass and/or moisture content of successive increments of the moving commodity or commodities.
Still another object of the invention is to provide a novel method of and novel apparatus for prolonging the useful life of the resonator housing.
A further object of the invention is to provide a resonator housing that is not affected or is not appreciably affected by the so-called skin effect which is a factor affecting the measurements carried out by apparatus employing conventional resonator housings.
Another object of the invention is to provide the apparatus with novel and improved materials for preventing corrosion of the internal and/or external surface of the resonator housing.
One feature of the present invention resides in the provision of an apparatus which can be utilized to ascertain the characteristics of moving elongated rod-shape commodities of the tobacco processing industry by exposure to microwaves. The apparatus comprises a resonator housing having an inlet for admission and an outlet for evacuation of commodities, and at least a portion of the housing consists of a material having a low thermal expansion coefficient. The exposure of commodities to microwaves takes place in an internal chamber which is disposed between the inlet and the outlet of the housing, and such exposure normally serves to ascertain the mass and/or the moisture content of commodities.
The material of the resonator housing can constitute an alloy, e.g., an alloy containing approximately 64% of iron and approximately 36% of nickel.
In the absence of any undertakings to the contrary, the temperature of the resonator housing varies or is likely to vary when the apparatus is in use. Therefore, the apparatus preferably further comprises a regulator for regulating the temperature of the housing; the regulator preferably maintains the temperature of the housing at least close to a preselected value in actual use of the apparatus. The regulator can comprise a thermometer which serves to generate signals denoting the temperature of the housing, and at least one transistor which is designed to dissipate (in response to signals from the thermometer) heat at a rate proportional to variations of the temperature of the housing. It is preferred to resort to a preselected value which is higher than the temperature of the atmosphere around the housing.
The internal chamber is preferably configurated in such a way that it is symmetrical with reference to the longitudinal axis of the rod-shaped commodity being moved through the internal chamber from the inlet to and through and beyond the outlet of the resonator housing. For example, the housing can be provided with an at least substantially cylindrical internal chamber.
The internal chamber can be, and preferably is, bounded at least in part by a corrosion resistant substance. Such substance can constitute a liner which surrounds a portion of or the entire internal chamber. The substance of the liner can contain at least one metal; for example, the liner can contain or can consist of gold. It is advisable to select the metal of the corrosion resistant substance in such a way that the latter is a good conductor of electric current.
It is further advisable to provide the resonator housing with a liner which consists of a corrosion resistant material and coats at least a portion of the external surface of the housing. Such external liner can contain or consist of gold.
The apparatus can be equipped with a protective tube which surrounds a path for the commodities being moved through the housing in a direction from the inlet toward the outlet. The protective tube can be made of or it can contain a suitable plastic material, for example, a polyaryletherketone and preferably a polyaryletheretherketone. In accordance with a feature of the invention, the protective tube has a receiving portion which is disposed at the inlet of the resonator housing and defines a passage which diverges in a direction away from the outlet.
The housing can be provided with an extension which surrounds the inlet and/or the outlet and serves to oppose issuance or escape of microwaves from the internal chamber between the inlet and the outlet of the housing.
Still further, the housing can comprise a tubular extension which is provided at the inlet and/or at the outlet, i.e., in the internal chamber, and which defines a portion of the aforementioned path for movement of commodities from the inlet to the outlet.
The apparatus further comprises microwave generator components for admitting microwaves from the generator into the internal chamber, preferably microwaves having at least two different frequencies, and a circuit having a comparator for comparing a first resonance curve which is influenced by the commodities in the housing with a second resonance curve which is not influenced by the commodities in the housing to thus ascertain a shift of frequency of the first resonance curve by the commodities. The circuit can further comprise a comparator for comparing the amplitudes of the first and second resonance curves for the purpose of ascertaining the extent of damping of the first curve by the commodities. The aforementioned different frequencies are preferably associated with a downwardly sloping flank of a resonance curve.
Another feature of the invention resides in the provision of an apparatus which serves to ascertain the characteristics of moving elongated rod-shaped commodities of the tobacco processing industry by exposure to microwaves. The improved apparatus comprises a metallic housing having an inlet for admission of commodities, an outlet for evacuation of commodities, and an internal chamber disposed between the inlet and the outlet to provide or establish a region for exposure of commodities to microwaves in order to ascertain at least one of (a) the mass and (b) the moisture content of commodities. The temperature of the housing is variable when the apparatus is in use, and the apparatus further comprises a regulator for regulating the temperature of the housing while the apparatus is in use. The regulator can be designed, assembled and operated in a manner as already outlined hereinbefore.
A further feature of the invention resides in the provision of an apparatus for ascertaining the characteristics of moving elongated rod-shaped commodities of the tobacco processing industry by exposure to microwaves. The improved apparatus comprises a metallic housing having an inlet for admission of commodities, an outlet for evacuation of commodities and an internal chamber which is disposed between the inlet and the outlet to provide a region for exposure of commodities to microwaves in order to ascertain the mass and/or the moisture content of commodities. The apparatus further comprises a corrosion resistant substance which bounds at least a portion of the internal chamber. The configuration, size and material of the corrosion resistant substance can be selected as already described hereinbefore.
An additional feature of the invention resides in the provision of an apparatus for ascertaining the characteristics of moving elongated rod-shaped commodities of the tobacco processing industry by exposure to microwaves. The apparatus comprises a metallic resonator housing having an inlet for admission of commodities, an outlet for evacuation of commodities and an internal chamber disposed between the inlet and the outlet to provide a region for exposure of commodities to microwaves to thus ascertain the mass and/or the moisture content of commodities. The improved apparatus further comprises a protective tube which surrounds a path for commodities being moved through the housing from the inlet, through the internal chamber and to and beyond the outlet. The material and the configuration of the protective tube can be selected in a manner and for the purposes as pointed out hereinbefore.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and the modes of constructing, assembling and operating the same, together with. numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.